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Date: Mon, 20 Apr 2015 23:42:59 +0000 (UTC)
From: "ASF GitHub Bot (JIRA)" <jira@apache.org>
To: issues@flink.incubator.apache.org
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Subject: [jira] [Commented] (FLINK-1297) Add support for tracking statistics
 of intermediate results
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    [ https://issues.apache.org/jira/browse/FLINK-1297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14503961#comment-14503961 ] 

ASF GitHub Bot commented on FLINK-1297:
---------------------------------------

Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/605#discussion_r28739333
  
    --- Diff: flink-core/src/main/java/org/apache/flink/statistics/heavyhitters/IHeavyHitter.java ---
    @@ -0,0 +1,37 @@
    +/*
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *     http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing, software
    + * distributed under the License is distributed on an "AS IS" BASIS,
    + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    + * See the License for the specific language governing permissions and
    + * limitations under the License.
    + */
    +
    +package org.apache.flink.statistics.heavyhitters;
    +
    +import java.util.HashMap;
    +
    +/**
    + * Interface for classes that track heavy hitters. It follows the same design as the interfaces from
    + * {@link com.clearspring.analytics.stream}
    + */
    +public interface IHeavyHitter {
    --- End diff --
    
    Interfaces do not follow a special naming convention in the Flink code base such as starting with a capital `I`. Please rename to `HeavyHitter` for consistency.


> Add support for tracking statistics of intermediate results
> -----------------------------------------------------------
>
>                 Key: FLINK-1297
>                 URL: https://issues.apache.org/jira/browse/FLINK-1297
>             Project: Flink
>          Issue Type: Improvement
>          Components: Distributed Runtime
>            Reporter: Alexander Alexandrov
>            Assignee: Alexander Alexandrov
>             Fix For: 0.9
>
>   Original Estimate: 1,008h
>  Remaining Estimate: 1,008h
>
> One of the major problems related to the optimizer at the moment is the lack of proper statistics.
> With the introduction of staged execution, it is possible to instrument the runtime code with a statistics facility that collects the required information for optimizing the next execution stage.
> I would therefore like to contribute code that can be used to gather basic statistics for the (intermediate) result of dataflows (e.g. min, max, count, count distinct) and make them available to the job manager.
> Before I start, I would like to hear some feedback form the other users.
> In particular, to handle skew (e.g. on grouping) it might be good to have some sort of detailed sketch about the key distribution of an intermediate result. I am not sure whether a simple histogram is the most effective way to go. Maybe somebody would propose another lightweight sketch that provides better accuracy.


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